1. Field of the Invention
The present invention relates to a particle and a near-field optical waveguide comprising a thin film formed with the particle.
2. Related Art
In recent years, particles (nanoparticles) having diameters of nanometer size have been synthesized by various methods, and those nanoparticles are being put into practical use. For example, JP-A 2007-148289 (KOKAI) discloses a technique for replacing electronic circuits with near-field optical waveguides of very small size exceeding the diffraction limit of light as the foundation of minute optical circuit construction. Attention is now being drawn to the nanoparticles used in the near-field optical waveguides. To use the nanoparticles to form a thin film for a waveguide, the nanoparticles may be deposited on a substrate, and etching may be performed to form a desired structure. In such a waveguide structure, however, the nanoparticles need to have quite high heat resistance.
It is known that the melting point of nanoparticles containing a metal normally becomes lower as the size of the nanoparticles becomes smaller. In view of this, a recent study has suggested that copper nanoparticles are turned into ink-like form, are applied onto a substrate, and are heated to form copper wiring. Even if the heating temperature is low, metal nanoparticles sufficiently melt to form bulk metal. Accordingly, formation of microorder wiring becomes possible (see Journals of Japan Institute of Electronic Packaging, Vol. 10, No. 5, p.p. 403-407, 2007, and Vol. 9, No. 7, p.p. 533-537, 2006, for example).
As mentioned above, the melting point becomes lower as the nanoparticles become smaller in nanometer size. Therefore, the use of those nanoparticles in the form of particles causes a problem in devices in terms of reliability in heat resistance. To counter this problem, there is a demand for rapid development of nanoparticles that have sufficient heat resistance while having a smaller nanosize diameter. By a method of forming metal wiring in an ink-jet manner with the use of nanoparticles, the organic substances are completely removed at a temperature of 250° C. Therefore, resistance to temperatures of 250° C. or higher is required. In semiconductor processing operations, 400° C. heating is often performed during the manufacturing procedures. To be used in such a semiconductor circuit, a near-field optical waveguide needs to endure 400° C.